This is a Letter to the Editor written by David Eoff of Preferred Utilities to Today’s Boiler regarding an article in the Spring 2018 edition called: Warning–A Boiler Breakdown may be in your Future story.
“As Geoff Halley, the author of this article stated, the low water cutout switches that prevent a boiler from dry firing are prone to failure, and require periodic maintenance and testing. Low water cutout float switches can become stuck due to accumulation of sediment on the float mechanism, or due to the float getting deformed and sticking against the side of the switch housing. Probe type low water cutouts can fail due to accumulation of sediment on the probes, broken wires, and malfunctioning relays. Both types of low water cutout devices can be wired wrong, or intentionally jumpered by boiler operators.
As a back-up to traditional, code required low water cutoff switches, Preferred Utilities recommends a high stack temperature cutoff be installed in all boilers. A high stack temperature cutoff set at 200-300 degrees F. over normal stack temperature will quickly shut the boiler down if it is dry fired, and is not likely to cause nuisance trips. The high stack temperature cutout usually consists of a thermocouple installed in the stack that reports back to the boiler flame safeguard controller. Preferred Utilities’ BurnerMate Universal and BurnerMate TS controllers have included this feature for decades. Preferred’s JC-15D stack temperature monitor will open a dry contact if the stack temperature goes above a pre-determined setpoint and can be added to virtually any flame safeguard system.
Several Preferred Utilities representatives and technicians have reported these high stack temperature cutoff devices have saved boilers from dry firing when the traditional low water cutoff switches failed. People who have experienced a close call like this insist on installing a high stack temperature cutoff on every future boiler.
A stack temperature thermocouple is inexpensive, reliable, reads constantly so you know the device is working, and requires no maintenance. It’s cheap, reliable insurance against a catastrophic dry firing event.”